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\begin{abstract}
Climate change has received much attention in recent years. The needs of prediction and validation of real systems behaviors and natural phenomena are critical. Simulation is a good candidate for this mission.\\
However, the major problem is that modeling and simulating complicated and large physical systems are time-consuming. Despite many commercial software now exist for such systems (water, forest modeling as examples), require a considerable knowledge of specific physical processes, and about the study areas. Thus, at the first step, we propose a practical way for simply modeling physical systems, especially natural system, by using Cellular Automata (CA). The PickCell tool developed at Lab-STICC laboratory will facilitate that process. As a point, GPU computations and parallelisms will be proposed as an important part of this methodology. The purpose is to accelerate large size physical simulations.\\
In addition, we propose the use of distributed simulations to deal with the lack of interoperability between simulations. To do that, we use an IEEE standard High Level Architecture (HLA) for designing the system supporting \textbf{mixed simulations} being based on synchronous systems. This also makes a great chance of conducting the simulations Cyber-Physical Systems.
\end{abstract}
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\section*{Acknowledgments}  
I would like to give special thanks to professor Bernard Pottier, and all of my colleagues at LabSTICC, UBO. I appreciate the supports not only in research activities but also in my daily life.\\[1cm]

\hfill Tran Van Hoang, Brest, France, \today

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